Advice on keg purchase?

[Funlovingfool]

I just finished building my first small 4 gallon pot still and have a few cleaning runs under my belt. Already I am enjoying this hobby and wanting to upgrade to something larger. So my next purchase is going to be a 13-15.5 gallon stainless steel keg. I have an ad on craigslist looking for one, but no luck so far. I see them on ebay, but folks advertise them for "homebrew" and want $100 or more. Although the description said stainless steel, some of the kegs sure look aluminum to me. Sooooo I've got a few questions concerning kegs:

1. Whats a fair price to pay for a used SS beer keg? Should I bite the bullet and pay the $100 on ebay or be patient and hope something comes up on craigslist?
2. Is there a certain type of keg that needs little or no modification to be used as a still? (Something easy to attach a head to with tri clover clamp)
3. Is there a certain type of keg "post" that I should look for or stay away from?
4. Will the kegs have writing indicating stainless steel or aluminum?
5. Are the valves/balls hard to remove?

Thanks for any help in advance. I'm trying to make sure I buy the right kind of keg that requires little or no modification to attach a copper lyne arm/column to it. Preferably using something like a tri clover clamp. I'm worried if I buy the wrong kind, I will not be able to mod it myself (I don't have torches,steel cutters,etc) and it will be useless.